The present disclosure relates generally to reducing electromagnetic effects from lightning strikes to aircraft structures containing composite components and metal components.
Aircraft often incorporate composite components in the fan section and compressor sections of a gas turbine engine to decrease the weight of the aircraft. Decreasing the weight of the aircraft increases the fuel efficiency of the aircraft and its payload capacity. Composite components are generally made by combining and curing carbon fibers within a resin matrix. Some of these composite components are connected within the gas turbine engine through a flange configuration that bolts a composite component between two metal components. Typically, the outer surface of the composite component electrically insulates the composite component and the carbon fibers within the composite component from the metal components disposed on either side of the composite component.
Because the carbon fibers within the composite component are electrically conductive, it may be necessary to electrically ground the composite component to at least one of the neighboring metal components to protect the composite component against lighting strikes. Lighting strikes can cause the carbon fibers in an ungrounded composite component to heat up beyond the pyrolyzation temperature of the resin matrix. When the resin matrix surrounding the carbon fibers exceeds its pyrolyzation temperature, the resin matrix surrounding the carbon fibers transforms into a heated pressurized gas that may lead to delamination of the composite component. One method that is used to electrically ground the composite component to a neighboring metal component is to attach a metal rivet to the composite component and extend a wire from the rivet to the neighboring metal component. This method is disadvantageous as it requires additional hardware and requires drilling an additional hole in the composite component to house the rivet and put the rivet in contact with the carbon fibers. Another method that is used to electrically ground the composite component to the neighboring metal component is to strip the outer layer on the composite component to expose the carbon fibers. The neighboring metal component is stripped of any insulating coatings, and the stripped surface of the metal component is positioned against the stripped surface of the composite component. This method is disadvantageous as stripping the outer layer of the composite component may affect its durability. This method also is disadvantageous as stripping the insulating coatings from the metal component may induce corrosion of the metal component.